The present inventions generally relate to radio communications and, more particularly, to multi-beam antennas utilized in cellular communication systems.
Cellular communication systems derive their name from the fact that areas of communication coverage are mapped into cells. Each such cell is provided with one or more antennas configured to provide two-way radio/RF communication with mobile subscribers geographically positioned within that given cell. One or more antennas may serve the cell, where multiple antennas commonly utilized are each configured to serve a sector of the cell. Typically, these plurality of sector antennas are configured on a tower, with the radiation beam(s) being generated by each antenna directed outwardly to serve the respective cell.
A common wireless communication network plan involves a base station serving three hexagonal shaped cells or sectors. This is often known as a tri-cellular configuration. In a tri-cellular configuration, a given base station antenna serves a 120° sector. Typically, a 65° Half Power Beamwidth (HPBW) antenna provides coverage for a 120° sector. Three of these 120° sectors provide 360° coverage. Other sectorization schemes may also be employed. For example, six, nine, and twelve sector base stations have been proposed. Six sector sites may involve six directional base station antennas, each having a 33° HPBW antenna serving a 60° sector. In other proposed solutions, a single, multi-column array may be driven by a feed network to produce two or more orthogonal beams from a single aperture. See, for example, U.S. Patent Pub. No. 20110205119, which is incorporated by reference.
Increasing the number of sectors increases system capacity because each antenna can service a smaller area. However, dividing a coverage area into smaller sectors has drawbacks because antennas covering narrow sectors generally have more radiating elements that are spaced wider than antennas covering wider sectors. For example, a typical 33° HPBW antenna is generally two times wider than a common 65° HPBW antenna. Thus, costs and space requirements increase as a cell is divided into a greater number of sectors.